Alternating signs of quiver coefficients

We prove a formula for the Grothendieck class of a quiver variety, which generalizes the cohomological component formulas of Knutson, Miller, and Shimozono. Our formula implies that the -theoretic quiver coefficients have alternating signs and gives an explicit combinatorial formula for these coefficients. We also prove some new variants of the factor sequences conjecture and a conjecture of Knutson, Miller, and Shimozono, which states that their double ratio formula agrees with the original quiver formulas of the author and Fulton. For completeness we include a short proof of the ratio formula.

     

Broadband heteronuclear Hartmann-Hahn sequences with short cycle times

For some applications, broadband heteronuclear Hartmann-Hahn sequences with very short cycle times are required. A quality factor is presented that makes it possible to assess the relative sizes of cycle time, bandwidth, and maximum RF amplitude for any given multiple-pulse sequence. This quality factor is determined for multiple-pulse sequences that are commonly used in HEHAHA experiments and for some favorable sequences that were so far only discussed in the context of heteronuclear decoupling.     

Spectra of BP-linear relations, -series, and BP cohomology of Eilenberg-Mac Lane spaces

On Brown-Peterson cohomology groups of a space, we introduce a natural inherent topology, BP topology, which is always complete Hausdorff for any space. We then construct a spectra map which calculates infinite BP-linear sums convergent with respect to the BP topology, and a spectrum which describes infinite sum BP-linear relations in BP cohomology. The mod cohomology of this spectrum is a cyclic module over the Steenrod algebra with relations generated by products of exactly two Milnor primitives. We show a close relationship between BP-linear relations in BP cohomology and the action of the Milnor primitives on mod cohomology. We prove main relations in the BP cohomology of Eilenberg-Mac Lane spaces. These are infinite sum BP-linear relations convergent with respect to the BP topology. Using BP fundamental classes, we define -series which are -analogues of the -series. Finally, we show that the above main relations come from the -series.

     

On copies of c 0 in the bounded linear operator space

In this note we study some properties concerning certain copies of the classic Banach space c ₀ in the Banach space of all bounded linear operators between a normed space X and a Banach space Y equipped with the norm of the uniform convergence of operators.     

A Banach space block finitely universal for monotone bases

A reflexive Banach space with a basis is constructed having the property that every monotone basis is block finitely representable in each block basis of .

     

BCH信道编码对降低快跳频OCDMA系统中色度色散的影响

提出BCH信道编码的方案来降低色度色散对降低快跳频OCDMA系统性能的影响.采用BCH信道编码后,单重合码的长度将变短,即可以用较少的波长数来构造码字,因此降低了色度色散的影响.分析结果表明,在相同的信息比特速率、脉元间隔、资用波长数的情况下,BCH信道编码能显著改善FFH-OCDMA系统的误码率性能.同时,由于单重合码的长度将变短,大大降低了光纤光栅的制作难度.由于BCH信道编码在电域中实现,其硬件技术已相当成熟,所以对整个BCH/FFH-OCDMA系统的代价影响不大.     

截短的单重合码对降低FFH-OCDMA系统差拍噪音的研究

在相同的系统结构下,提出一种截短的单重合码来有效降低差拍噪音对快跳频光码分多址(FFH-OCDMA)系统误码率性能的影响,并对其进行了理论分析和数值模拟.结果表明,当同时用户数较多时,该方案能显著改善FFH-OCDMA系统的误码率性能.     

On the spectrum of almost periodic solution of second order scalar functional differential equations with piecewise constant argument

We study the spectrum containment of almost periodic solution to neutral delay differential equations with piecewise constant argument (EPCA, for short). We find an important property, which is different from that given by Cartwright for ordinary differential equations (ODE). Some known (periodic solution) results would be expanded. As a corollary, it is shown that EPCA with periodic perturbations possess a quasi-periodic solution and no periodic solution. This new phenomenon is due to the piecewise constant argument and illustrates a crucial difference between ODE and EPCA.